In the field of mobile communications technologies, a beam at a transmit end of a base station is often adjusted in a horizontal dimension, and a downtilt angle is fixed for each terminal in a vertical dimension. Therefore, various beamforming and precoding technologies are all based on channel information in the horizontal dimension. Because a channel is three-dimensional (3D), an optimal throughput of a system cannot often be achieved by means of a method of a fixed downtilt angle. Therefore, beam adjustment in the vertical dimension is very important to improvement of system performance. A technical concept thereof mainly is: a 3D beamforming weighted value at an active antenna end is adjusted according to 3D channel information estimated by a terminal, so that a main lobe of a beam is “aligned to” a target terminal in 3D space, so as to greatly improve received signal power, and improve a signal to interference plus noise ratio, thereby improving a throughput of an entire system.
A 3D beamforming technology is based on an active antenna system (AAS) currently, and compared with a conventional antenna (for example, a 2D antenna array), an active antenna further provides a degree of freedom in a vertical direction. Therefore, a system capacity can be improved.
Currently, a measurement mechanism for channel state information (CSI) is mainly specific to a conventional antenna, and when the measurement mechanism is applied to an AAS antenna, measurement accuracy can hardly be met.